The baffles go in from the slash cut end, just imagine inserting the baffle, narrow end first, into the can whils't it is still on the bike (not that I did).
The wide end of the baffle is 48mm with a VERY slight flange on the end. The ProRace exhaust has a 48mm internal diameter so the baffle is a nice snug fit, hence the reason I put a piece of wood on the flange end and tapped it very lightly
to encourage it to go in. It stops itself from going too far because of the flange.
As said, make sure before you tap it in that the fixing bolt hole is lined up with the bottom of the ProRace. I then just sat it on the bench and eyed the drill into line with the bolt hole and drilled the hole. I put a 3mm pilot hole in first to check alignment and then opened it up to a 6mm hole for the bolt.
It really is a simple job. And due to the crap weather I still haven't tried it out